The present invention pertains to a system, operable with the instruments of an aircraft, particularly a slow-moving aircraft, for inflight training in the use of laser and/or electronic warfare countermeasure equipment and tactics. More particularly, the system of the present invention operates the instruments of the aircraft to present threats to the aircrew according to whether the aircraft is within range, and within the line-of-sight of the threat.
It is believed that systems for providing inflight training to pilots and/or aircrews in electronic warfare equipment and tactics generally have followed one of two approaches. The first general type are those systems employing one or more stationary radar signal emitters to simulate the signal characteristics of a particular threat. In this family, the systems frequently require activation of the entire radar warning receiver system in the aircraft. The other type of system differs from the first by generally eliminating to ground based emitters to provide a self-contained, signal generating unit aboard the aircraft.
U.S. Pat. No. 4,176,468 provides at least a general description of each of the latter types of training systems. Illustratively, systems of the first type employ signal transmitting and receiving stations and include an air combat maneuvering range having a ground-based control station, at least one training craft and of course, the plurality of signal transmitting and receiving stations. The aircraft's position is computed by multilateration using at least three of the emitting/receiving stations. When the aircraft is in the proper geographical position and altitude to detect the threat, the ground station activates onboard maneuvering instrumentation and equipment which in turn controls the radar warning receiver to provide audio and visual cues accordingly. The pilot's reactions to the threats are then monitored at the ground display and control station.
Also illustrative of earth-based simulator systems is U.S. Pat. No. 4,057,913 wherein a computer on board the aircraft receives flight parameter data from the aircraft's instruments and transmits this data to a ground based simulator station. The simulator station remotely controls one or more sonobuoy transmitters which in turn produce target signals, emulating the signal produced by a submarine or surface vessel. According to this patent, the aircraft's flight crew recognizes no difference between the signals produced by the sonobuoys and the signals generated by an actual enemy target.
The prior art recognizes that systems of the emitter type have various shortcomings such as unusually high cost and complexity. Further, such systems are said to emit large amounts of electromagnetic radiation so as to interfere with local television and radio communications, and, that such strong electromatic fields are said to be easily monitored by hostile powers, thus compromising the security of those systems. Finally, it is said that such systems require complex communication networks between the ground control stations, the threat mimicking stations, and the aircraft.
To overcome some of such shortcomings, U.S. Pat. No. 4,176,468 discloses a system of the type where the threat mimicking radar stations are eliminated. The stations are replaced by a threat instruction receiver and a threat simulator, both carried aboard the aircraft. The equipment aboard the aircraft is programmed by the ground-based control station.
Systems wherein all or substantially all of the equipment is carried aboard the training aircraft are suitable for fighter or other relatively fast moving aircraft. However, such systems are very unsatisfactory for slow-moving aircraft such as helicopters. Often, systems of the second general type rely on preprogrammed values to ascertain the "line-of-sight" between an electronic warfare threat and the aircraft. For example, the line-of-sight determination is made by electronically deriving the aircraft's position and comparing this position with threat locations and training area terrain features, all of which are preprogrammed into on-board memory before the commencement of combat training maneuvers.
Errors in determining the aircraft's precise position, and, errors in the preprogrammed parameters however, could compound to result in aggregate errors of several hundreds of feet in the line-of-sight determination. Such errors are intolerable for helicopter training where the helicopter crew must be trained to fly very low to the ground and to hover behind ridges or other high terrain in order to avoid exposure to various laser or electronic warfare threats. Thus, for the purposes of training the crews of helicopters and other slow-moving aircraft in countermeasure tactics for electronic warfare, exact line-of-sight simulation must be provided. Such training, as will be appreciated, is also very useful for inflight training in relatively fast moving aircraft.